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State the concept of normalization.

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Normalization

Normalization is the process of organization data in a database to reduce the redundancies. The process of normalization includes both creating tables and establishing relationship between those tables using rules designed to protect the data and to make the database more flexible. These goals are achieved by eliminating both redundancies in the data fields as well as the inconsistent dependency between various fields. The data is said to be redundant if same data is found in more than one place in a table. The following figure illustrates the unnormalized and normalized database.


Fig: Next stage of normalized table
When a person makes a phone call, the caller's information is stored in the table. If the same person makes a phone call next time, LastName, FirstName, Birthday, HomePhone, HomeCity, HomeStreet of the caller is same as previous attempt. Only, DateOfCall and CallDescription may be different. So, the table is broken down into two, Contact table for the repeating fields and Note table for non repeating fields. The Note table consist of three fields contact (ii) Dateofcall and calldescription. Also, if the same person makes a call on the same day twice, record Dateofcall is also a repeating field. For example, the caller may have made a personal call in the morning and a business call in afternoon. So, the Calldescription field is placed in separated table CallType relating by a field calltypeID.

Types of Normalization
  1. First Normal Form (1NF)
  2. Second Normal Form (2NF)
  3. Third Normal Form (3NF)
  4. Boyce clod Normal form (BCNF)
  5. Fourth Normal Form (4NF)
  6. Fifth Normal Form (5NF)




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